The present invention relates to the formation of a polyurethane-polyvinyl ester composition and to a process for forming the same utilizing ultraviolet light initiated polymerization of free radical polymerizable monomers and oligomers. The composition can then be utilized in forming laminates which can be applied to an end product as by thermoforming.
Heretofore, it has been desirable to apply highly crosslinked coatings to the decorative laminates since such coatings exhibit good durability properties such as abrasion resistance and mar resistance as well as increase chemical resistance to solvents and cleaners. A common application for such decorative laminates involves thermoforming the laminate which desirably has a PVC substrate to an end product such as a molded part. However, such highly crosslinked coatings are subject to cracking after they are stretched during the thermoforming process.
U.S. Pat No. 5,780,117 relates to radiation-curable latex compositions having a secondary curing mechanism. In these compositions, an anionically stabilized, water-borne dispersion of one or more radiation-curable resins is combined with a low molecular weight compound having at least two reactive functional groups, wherein one reactive functional group comprises an epoxy and the other reactive functional group comprises either an epoxy or a functionality capable of self-condensation after film formation. Also disclosed is a method for providing a cross-linked protective coating on a substrate, wherein a coating of the composition of the present invention is applied to the substrate, the coated substrate is exposed to actinic radiation to effect curing, and then the unexposed or underexposed portions of the coated substrate are allowed to cure at room temperature or greater.
European Disclosure 00331409 relates to a process for producing a polyester film having a thin cured polyurethane coating, which comprises (1) applying an aqueous composition comprising a thermosetting polyurethane prepolymer as a film-forming component to at least one surface of an unoriented aromatic polyester film to form a thin wet coating on it, said polyurethane prepolymer being characterized by (i) having a polyol component at least 10% by weight of which is composed of a polyol containing a carbon-carbon double bond selected from unsaturated polyester polyols and polybutadiene polyols, the carbon-carbon double bond being cleavable under ultraviolet light, (ii) having a pendant anionic hydrophilic group in the polymer chain, and (iii) having isocyanate groups blocked with an oxime at the ends of the polymer chain, and (2) thereafter stretching and heat-setting the coated film, during which time the wet coating of the aqueous composition is dried and the polyurethane prepolymer is cured to form a thin cured polyurethane coating having a carbon-carbon double bond on the biaxially oriented polyester film.
U.S. Pat. No. 4,107,013 relates to an improved ultraviolet curable aqueous latex paint suitable for use as coil coatings comprising a high molecular weight primary latex binder in combination with minor amounts of an emulsified low molecular weight cross-linking agent adapted to cross-link the high molecular weight latex particles upon exposure to ultraviolet energy.
The composition of the present invention generally comprises a co-mingled polyurethane-polyvinyl ester composition, which has improved thermoforming properties, and has good flexibility, good scratch and abrasion resistance, and can have low gloss when containing flattening agents. The composition is derived from a waterborne polyurethane to which is added a free radical, radiation polymerizable monomers or oligomers such as various acrylates. A photoinitiator is desirable utilized in order to permit the free radical polymerizable monomers to be polymerized by ultraviolet light. Optionally, a urethane thermal-crosslinking agent can be added to the waterborne polyurethane. Generally, the aqueous polyurethane is coated on a substrate such as plastic or paper and dried in order to eliminate water. The free radical monomers or oligomers are then cured by radiation such as UV light to form a laminate. The laminate can then thermoformed onto an end product generally under heat.